From obesity to oncology; bariatric surgery and the impact on breast cancer- what is the link? – A systematic review and meta-analysis

Background: Obesity is a complex, progressive and relapsing chronic disease associated with significant medical complications, such as breast cancer. Bariatric surgery is currently the most effective treatment modality for obesity. This systematic review and meta-analysis examined the incidence of breast cancer in those who underwent bariatric surgery, as well subgroup analysis focusing on the effect of menopausal status in this cohort. Methods: This systematic review and meta-analysis was conducted in accordance with PRISMA guidelines, involving the search of databases including Cochrane Library, Embase, Scopus, Pubmed and Google Scholar. The quality of the studies was assessed using the Newcastle-Ottawa scale (NOS). Statistical analysis was performed using Review Manager (Revman) Version 5.4. Results: A total of 2,288,003 patients with obesity were included in the analysis. There was a statistically significant risk reduction in breast cancer incidence in those who underwent bariatric surgery compared to those who did now (RR 0.58 95 % confidence interval (CI) 0.46, 0.72, p < 0.001) across all fourteen studies. There was significant heterogeneity across the studies (Chi2 = 358 p < 0.00001, I2 = 96 %). Further subgroup analysis was performed on four of the included studies regarding the impact of menopausal status on breast cancer incidence. There was no statistically significant reduction in premenopausal breast cancer risk (RR 0.88 95 % CI 0.74, 1.04). The result was similar in the postmenopausal cohort (RR 0.46 CI 95 % 0.18, 1.19). Conclusion: This systematic review and meta-analysis demonstrates that bariatric surgery is associated with a statistically significant reduction in breast cancer incidence by pathways alluded to in this review and likely by a number of mechanisms yet to be fully elucidated. The role of menopausal status on breast cancer incidence in those who undergo bariatric surgery remains unclear.